/*
 *  Copyright 2011 Yuri Kanivets
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package kankan.wheel.widget.adapters;

import java.util.LinkedList;
import java.util.List;

import android.database.DataSetObserver;
import android.view.View;
import android.view.ViewGroup;


/**
 * Abstract Wheel adapter.
 */
public abstract class AbstractWheelAdapter implements WheelViewAdapter
{
   // Observers
   private List< DataSetObserver > datasetObservers;
   
   

   public View getEmptyItem( View convertView, ViewGroup parent )
   {
      return null;
   }
   


   public void registerDataSetObserver( DataSetObserver observer )
   {
      if ( datasetObservers == null )
      {
         datasetObservers = new LinkedList< DataSetObserver >();
      }
      datasetObservers.add( observer );
   }
   


   public void unregisterDataSetObserver( DataSetObserver observer )
   {
      if ( datasetObservers != null )
      {
         datasetObservers.remove( observer );
      }
   }
   


   /**
    * Notifies observers about data changing
    */
   protected void notifyDataChangedEvent()
   {
      if ( datasetObservers != null )
      {
         for ( DataSetObserver observer : datasetObservers )
         {
            observer.onChanged();
         }
      }
   }
   


   /**
    * Notifies observers about invalidating data
    */
   protected void notifyDataInvalidatedEvent()
   {
      if ( datasetObservers != null )
      {
         for ( DataSetObserver observer : datasetObservers )
         {
            observer.onInvalidated();
         }
      }
   }
}
